nbd: disallow nbd-server-add before nbd-server-start
It works nicely with the QMP commands, but it adds useless complication
with HMP. In particular, see the following:
(qemu) nbd_server_add -w scsi0-hd0
(qemu) nbd_server_start -a localhost:10809
NBD server already exporting device scsi0-hd0
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index e362572..d1721a3 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -82,6 +82,11 @@
NBDExport *exp;
NBDCloseNotifier *n;
+ if (server_fd == -1) {
+ error_setg(errp, "NBD server not running");
+ return;
+ }
+
if (nbd_export_find(device)) {
error_setg(errp, "NBD server already exporting device '%s'", device);
return;
